Lockstitch sewing machine



.Furme E7, 1941. c F. RUBEL LOCKSTITCH SEWING momma Filed Aug. 18, 1937 5 Sheets-Sheet 1 r l I l l l I I LN UQNRN INVENTOR- Charles F Rubei,

W] TNESSES A TTORNEYS.

' June 17, 1941. c, F, RUBEL 2,246,010

LOCKSTITGH SEWING MACHINE Filed Aug. 1 8, 1937 5 Sheets-Sheet 2 m mm $1 Q i\ W1 TN ESSES I N VEN TOR.-

(fi Charles f RuZwL, MW ATTORNEYS.

June 17, 1941. c RUBEL 2,246,019

I LOCKSTITCH SEWING MACHINE Filed Aug. 18, 1937 5 Sheets-Sheet s FIG H INVENTOR: Char Z55 1? Babe] 7 WI TNESSES;

June 17, 1941. c. RUBEL 2,246,910

LOCKSTITCH SEWING MACHINE Filed Aug. 18, 1937 5 Sheets-Sheet 4 rj'vlllll/vlllln' will/If 111/11, A,

W1 TNESSES;H J9 INVENTOR;

A TTORN E YS.

June 17, 1941. g, RUBEL 2,246,010

I LOCKSTITCH SEWING MACHINE Filed Aug. 18, 1937 r 5 Sheets-Sheet 5 I N V EN TOR:

WITNESSES.-

Uharlas i Rube],

Patented June 17, 1941 LOCKS TITCH SEWING MACHINE Charles F. Rube], Chicago, Ill., asslgnor to Union Special Machine Company, Chicago, Ill., a corporation of Illinois Application August-18, 193%, Serial No. 159,646

21 Claims. 01. 112-181) This invention relates to high-speed sewing machines of the type wherein a complemental stitch-forming mechanism including a rotary hook component cooperates with a needle in forming what are ordinarily known as lockstitch seams. In such sewing machines as ordinarily constructed, the circumferential rib on the bobbin case holder engages the internal receiving groove in the rotary hook component with a snug working fit both circumferentially and laterally. As a consequence, excessive heat develops through friction between the relatively large contacting surfaces of the rib and the groove with the result that these parts wear very rapidly when the sewing machine is operated at high speeds. Special lubricating devices and cooling devices have been devised to lessen the frictional heat thus developed. Upon development of looseness due to wear to the extent that the needle thread is pinched between the inner side of the rib and the contiguous face of the groove, complete replacements of the worn parts may be required at a very considerable expense. The above difflculties are in part overcome by the construction disclosed in copending applications Serial No. 123,180, filed by me on July 30, 1936, and Serial No. 92,540, filed by me jointly with Clarence C. Smith on July 25, 1936, wherein, in both instances the rib on the bobbin case holder is considerably narrower. than the receiving groove in the rotary hook so that the bobbin case holder is normally permitted to fioat axially; and wherein a steadying element is provided which normally opposes the outward thrust of.

the said holder and which moves the latter inward, during each stitch-forming cycle, to bring the rear face of the rib into close proximity with the corresponding face of the groove in order to preclude pinching and rupturing of the needle thread during the critical period when the inner limb of the needle loop is engaged by the detaining shoulder or horn of the rib and lies crosswise of the groove with a portion thereof extending substantially parallel with the inner face of said groove. The steadying element of the first mentioned application contacts with the front, of the bobbin case at a single point to one side of the rotary hook axis; while in the second-mentioned application contact is made at two spaced points, but likewise to one side of the bobbin case axis. Thus in either of these constructions, when the bobbin case holder is free to float (as during the greater portion of each active rotation of the hook and throughout each idle rotation thereof) it is likely to cant and wobble relative to the axis of the rotary hook component so that, the side edges of its rib contact alternately with the contiguous faces of the groove in the rotary hook component with causation of considerable wear between them.

My present invention has for one of its objects to remedy this difficulty, which desideratum I realize in' practice as hereinafter more fully disclosed, through provision of a movably-mounted steadying element which is arranged to contact with the front of the bobbin case during the floating periods of the bobbin case holder,

'at several (at least three) substantially uniformly spaced circumferential points so that said holder cannot tilt as heretofore thereby precluding wear from this cause.

Another object of my invention is to attain all the foregoing advantages with a steadying element which is actuated from the feed mechanism of the sewing machine. v

A further aim of my invention is to minimize friction between the circumferential surfaces of the rib and the groove respectively of the bobbin case holder and the rotary hook component, which objective I also attain as hereinafter more fully set forth, by making the diameter of the rib slightly less than that of the groove so that the bobbin case holder can float up and down as well as axially with bearing contact existing between the rib and the groove only at a single circumferential point at any time. By reason of these changes, very little heating occurs between the rib and the groove even in the absence of lubrication and cooling, so that the transverse oil slits such as are usually provided in the rib may be entirely dispensed with.

Another object of my invention is to preclude intersections with the groove, of the screws which are used to secure removable circumferential portons (such as the gib which provides the loop releasing tail) of the rotary hook component to the body of said component, so that said groove is left with a smooth continuous non-wearing surface.

Other objects and attendant advantages Will appear from the following detailed description of the attached drawings, wherein Fig. I is a fragmentary view in plan of a sewing machine conveniently embodying the present improvements, a portion of the work support of the machine having been broken out to expose the underlying complemental stitch-forming and feeding mechanisms.

Fig. II is a cross sectional view of the machine taken as indicated by the arrows II--IIin Fig. I.

Fig. III is a fragmentary detail sectional view in axial section taken as indicated by the arrows IIIIII in Fig. V on a somewhat larger scale, of the complemental stitch-forming mechanism.

Fig. IV is a similar view looking in the opposite direction and taken as indicated by the arrows IVIV in Fig. V.

Fig. V is a sectional view taken as indicated by the arrows V-V in Figs. III and IV.

Fig. VI is a fragmentary detail sectional view taken as indicated by the arrows VI-VI in Fig. V. v

' Fig. VII is a 'view like Fig. V with the rotary hook component of the complemental stitchforming mechanism in a different position.

Fig. VIII is a view corresponding to Fig. IV with the rotary hook component of the complemental stitch-forming mechanism differently positioned.

Fig. IX is a detail sectional view taken as indicated by the arrows IXIX in Fig. VIII;

and

Fig. X is a perspective view of the steadying element hereinbefore referred to.

The sewing machine herein illustrated for convenience of exemplifying my invention has a horizontal work support I with a removable throat plate 2. Operative, through an opening 3 in the throat plate 2, to upwardly engage the material M (Fig. V) being sewed in the machine, and to intermittently advance it on the work support I is a feed dog 4 which is opposed from above by a presse'r foot 5 having a pivotal connection at 6 with a shank member I at the lower end of a presser bar 8. The vertically-reciprocating needle 9 of the machine is actuated, by suitable mechanism (not illustrated) from above the work support I and adapted, as is usual, to pass down through the throat plate 2 and to cooperate in a well known manner with the complemental stitch-forming mechanism comprehensively designated III to form a lockstitch seam. As shown, the feed dog 4 is mounted on the top of a cantilever I I which overreaches the complemental stitch-forming mechanism III and which has a vertically-slotted pendant shank I2 secured, by means of a clamp screw I3, to the outer end of a feed bar I5. Due to this arrangement, the feed dog 4 can be adjusted vertically on the feed bar as desired or required. The rear end of the feed bar I5 is pivotally connected at I6 to the top end of a rocker I! on a rock shaft I8 whereof the ends are engaged in pendant lugs I8, 20 of the work support I. Up and down or lift movements are imparted to the feed dog 4 from a shaft 2I extending longitudinally of the machine beneath the work support I and journaled in suitable fixed bearings, one of which is shown at 22 in Fig. I. At its front end, the shaft 2I has a small crank 23, which by means of a drop link 24, is coupled at 25 with the lower end of a downward projection 26 of the feed bar I5 in line with the shank I2 of the cantilever II, see Fig. II. Horizontal back and forth or feeding movements are also imparted to the feed dog 4 from the shaft 2I through means including an eccentric actuator 21 on said shaft having an associated strap 28 whereof the rod 29 is composed of two telescopically-interengaging sections 29a,

29b, the latter of these components being pivoted 60 to the rocker II at 30. By means of a drop link or lazy bar 3|, the strap rod section 2% is coupled with an arm 32 on a regulating shaft 33 extending parallel with the shaft 2| and journaled in suitable bearings (not shown) beneath the work support I. By rotatively adjusting the regulating shaft 33, the throw or feeding movement of the feed dog 6 may be varied to increase or decrease the stitch length, after the manner set forth in U. S. Patent No. 2,053,508, granted to George Sauer and Clarence C. Smith on March 31, 1936. One of the characteristics of this type of feed mechanism is that adjustment for stitch length or for reversal does not cause any change in the timing between the movements in the feed bar I5 and the needle 9.

Except as particularly pointed out later herein,

the complemental stitch-forming mechanism III 5 is generally similar to that featured in the copending applications Nos. 123,180 and 92,540 previously referred to in that it comprises an axiallyhollow rotating component or rotary hook 36 with a needle thread loop-engaging beak 31, a

loop receiving notch 38 between said beak and an over-reaching guard spur 39, and a loop-releasing tail 40; a frontally-open axially-hollow non-rotating component or bobbin case holder H which occupies the hollow of the rotary hook component; a removable bobbin case 42 with a needle-clearing notch 43 at the top, which fits into the hollow of the bobbin case holder; and a bobbin 44 which in turn fits into the hollow of the bobbin case. The rotary hook component 36 is formed at the rear with an axial boss 45 and is secured, by means of screws 46 passing through said boss, to another longitudinal shaft 41 in a bearing 48 integrally formed with the bearing 22 beneath the work support I. Through suitable gear connections (not shown) the shaft 41 is driven at double the speed of the shaft 2| so that the rotary hook component 36 revolves twice during each feeding movement of the feed dog 4 and during each reciprocation of the needle 9. As ordinarily, the face flange 49 of the bobbin case holder H is formed with a vertical frontal notch 50 at the top for engagement by the lateral projection 5| of a rotation-restraining finger 52 secured by screws 53 (Figs. I and II) to the under surface of the work support I, there being sufficient clearance between the notch and the lug as required to permit free reeving of the needle thread T, (see Figs. IV and VII) between them as the needle loop passes around the bobbin case holder M. It is to be noted that the width of the circumferential rib 55 on the bobbin case holder H is considerably narrower than the internal receiving groove 56 in the rotary hook 36 so that said holder is held assembled with the hook with freedom to normally float axially as in the two applications supra. As usual, the

rib 55 is interrupted at 51 with provision of a loop detaining horn 58. However, in accordance with my present invention the diameter of the rib is made somewhat smaller than the diameter of the groove in the rotary hook component 36 (see Fig. DI), so that peripheral contact between the rib and the groove occurs but in a single point at the bottom, with the result that the heating 55 effect is practically eliminated and lubrication therefore is made entirely unnecessary. As a consequence of this construction, the bobbin case holder H is allowed limited up and down play,

i. e., in a direction transversely'of the axis of the rotary hook component 36 to the advantage of further decreasing friction, in addition to limited axial play as already explained. A gib 60 is secured to the rotary hook component 36 by three screws 6| (Fig. I) which in accordance with my invention and as shown in Fig. VIII, clear the groove 56 so that the latter is left with a continuous smooth bearing surface for contact with the rib 55. The gib 60 provides the loop releasing tall 80, and. as illustrated, has a forward cam projection 62 which serves as a guard for the needle 9 to prevent the latter from fouling the bobbin M in the event that it is deflected or bent inwardly toward said hook component by conflict with a,cross seam or other abnormal thickness 7 variation in the material. The needle guard means just described constitutes the subject matter of another patent application Serial No. 159,645 filed by me concurrently herewith.

FromFigs. I, III, IV and IX, it will be observed that in accordance with my invention the bobbin case 42 is formed with a tri-spoked frontal face with the spoke arms substantially uniformly spaced angularly and with its downward spoke somewhat longer than the others so that it can be readily grasped for convenience in removing the bobbin case. The upper part of the bobbin case 42 is beveled as at 63 and the lower part oppositely beveled as at 64; while the portion forming the downward spoke is perfectly flat, and vertical. Disposed in contiguous relation to the face of the bobbin case 42 is a steadying member or element 65 having the form of a tri-arm with its arms arranged to correspond with the spokes of said bobbin case. As shown the steadying element 65 has substantially hemispherical spot projections 66, 61 on its two upper arms adapted to coact with the upper beveled surface 63 of said bobbin case 42 and with a narrow cam-like spot projection 68 On its downward arm (see Fig. X) adapted to coact with the lower beveled surface 64 on said bobbin case. The spot projection 66, it will be noted, is located above the axis of the rotary hook 36 at the downwardly-moving side of the latter considered with regard to its normal direction of rotation, that is to say, it lies substantially in a plane a-a (Fig. VII) which is radial to the hook axis and which extends through the end of the needle loop detaining horn 58 on the non-rotating bobbin case holder 4|. It will be further observed that the three spot projections 66, 61 and 68 are substantially. equally spaced circumferentially of the element 65. As shown in Figs. I, III, IV, VIII and X, the steadying element 65 is moreover formed with a forwardlyprojecting cylindric shank 69 which is fixed by a set screw in a boss I! at the outer end of an arm l2 fulcrumed for horizontal pivotal movement under the influence of a torsion spring 13 about a screw stud 15 on the feed bar I5. The arm '12 is normally maintained in the position shown in Figs. I and II by a latch hook T6 pivotally connected at TI to one side of the downward projection 26 of the feed bar 15 and held in locked position by the latch hook spring 18. By depressing the latch hook I6, the arm 12 and the steadying element 65 carried by it will be swung outward away from the complemental stitchforming means In by the torsion spring 13 when access is required to the front of the bobbin case holder 4| for removal of the bobbin case '12 and interchange of bobbins. By means of a' regulatable stop screw 79 engaged in the boss H of the arm 72, it is possible to accurately adjust the steadying element 65 for position in relation to the complemental stitch-forming mechanism Ill.

The stitch-forming cycle of my improved sewing machine is as follows: As a consequence of its connection to the feed bar 55, orbital movement is induced in the steadying element 65 in a plane parallel to that of the bobbin case holder ll, with the result that the spot projections 66, 61 and 68 are caused to trace small irregular elliptic paths indicated in dot-and-dash lines in Figs. V and VII. At the beginning of the active rotation of the rotary hook member 36 in the direction indicated by the arrows in the drawings during each stitch-forming cycle, immediately after the needle 9 has penetrated the material M, the needle thread T is engaged in a well known manner by the hook beak 31 and directed into the throa 38 by coaction of the guard spur 39 as shown in gs. III and V. At the same time, the inner limb L of the needle loop L is intercepted by the shoulder 58 of the rib and resting on the peripheral surface of the bobbin case holder 4|, witha portion thereof lying substantially parallel to the inner side of said rib and the corresponding inner side of the groove as shown in Figs. III and V. As the rotary hook component continues in its rotation, the outer limb L of the needle thread loop freely passes the spot projection 66 of the steadying element 65; while the spot projection 61 (which at this time is slightly lower on coacting bevel 63 of the bobbin case 42) holds said bobbin case and the holder 4| inward with the rib 55 on the latter substantially in contact with the rear face or circumferential shoulder of the groove 56 as shown in Fig. IV to insure against pinching and rupturing of the rear limb L of the loop. As the rotary hook component 36 continues further in its rotation, the front limb I. of the loop L passes between the spot projection 68 of the steadying element 65 and the bottom bevel 64 of the bobbin case 42 and thus operates to keep the latter and the bobbin case holder 4| pressed inward. By the time the loop L has reached the position shown in Fig. VII, the spot projection 68 has moved up to the flat vertical surface .of the downward spoke of the bobbin case 42 and continues to prevent the rib 55 from contacting with the front side of the groove 56 as the limb L passes the spot projection 61. Immediately upon passage of the spot projection 61 by the limb U of the loop, the bobbin case holder 4| is drawn outward as the slack in the thread T is absorbed by the take up (not shown) of the machine, to the end that the bobbin case 42 falls back upon the steadying element 65 as in Fig. VIII with prevention of contact between the rib 55 and the front side of the groove 56 and re-establishment of normal clearance between the said rib and the rear face or shoulder of said groove. The bobbin case 42 and its holder 4| remain in the position last described during the completion of the instant rotation of the rotary hook component 36 as well as during the entire succeeding idle rotation of said component. The above described operation is of course contingent upon accurate adjustment of the steadying element 65 in the arm 12 such that the needle thread T is permitted to pass between the projections 66-68 and the bobbin case 42 without undue restraint. It will be apparent that under the action of the steadying element 65, the bobbin case holder 4| is moved inward only during a Portion of each stitch-forming cycle with the rib 55 positioned at all other times approximately halfway between the front and rear sides of the groove 56 out of contact with them. By virtue of having its spot projections substantially uniformly spaced circumferentially with respect to the bobbin case 42, the bobbin case holder 4| is held true, that is to say, prevented from canting relative to the axis of the rotary hook component 36, with preclusion of wobbling and vibration of the latter regardless of the speed at which the machine is operated. Due to the smaller diameter of the rib 55, circumferential contact of the same with the bottom oi the groove 56 (which, as before stated, is smooth and continuous in view of the lateral oilsetting of the gib screws 6| beyond the plane of the groove) occurs only in a single point of tangency at any time irrespective of the position said holder may take in adapting itself to the action of the needle thread loop during stitch formation. Under these conditions, and since the rib 55 is substantially free of contact with the walls of the groove 56 at all times, very little friction takes place between them even at very high speeds, and they need not therefore be lubricated. This is highly advantageous, not only in that it precludes clogging of the mechanism by lint which tends to cling to and gather upon oiled surfaces, and-further in that it enables me to dispense entirely with the usual transverse oil grooves or slots in the rib of the bobbin case holder. Due to the smoothness and continuity of the periphery of the rib on the bobbin case holder and the capacity of said holder to float up and down, i. e., transversely of its axis, it will be apparent that escapement of the needle thread under the pull of the take-up of the machine can take place completely at any time after the needle thread loop has passed the lowermost point of the rotary hook. In other words, from that point on, except for the thread retaining tail or point, there is nothing to prevent the needle thread from being drawn up tight at any time after the needle loop has been completely distended. The possibility for the needle thread to be caught and ruptured is thus entirely precluded. Since the timing between the needle 9 and the feed bar l remains unchanged by adjustments of the feed mechanism for stitch length or for reversal as already pointed out hereinbefore, it also follows that the instant for taking up the axial play between the bobbin case holder and the rotary hook by the member 4| will always occur at the same time during each stitch forming cycle.

From the foregoing it will be apparent that I have provided, in a lockstitch sewing machine, a complemental stitch-forming mechanism in which the bobbin case holder is free to float up and down (in a direction transversely of the axis of the rotary hook component) and also axially relative to said hook component, and in which steadying means operates to control the bobbin case holder in such manner that friction between the latter and said rotary hook component is reduced to a minimum, so that the machine can be operated at much higher speeds than possible with complemental stitch-forming mechanism of ordinary construction.

Having thus described my invention, I claim:

1. In a. lockstitch sewing machine, stitch-forming mechanism including two relatively rotating components which are interconnected with capacity for limited axial play relatively; and a steadying element with at least three substantially uniformly-spaced circumferentiallyarranged spot projections adapted to oppose end thrust of one of said components thereby preventing it from canting with respect to the axis of the other component.

2. In a lockstitch sewing machine, stitch-forming mechanism including two relatively rotating components which are interconnected with capacity for limited axial play relatively; a steadying element with at least three substantially uniformly-spaced circumferentially-arranged spot projections adapted to cooperate with one of said components to normally oppose its end thrust and prevent it from canting in respect to the axis of the other component; and means for actuating the steadying element to reduce the axial play between the two components during a portion only of each stitch-forming cycle.

3. In a lock-stitch sewing machine, stitch-forming mechanism including a rotating component and a, non-rotating component; means interconnecting said components with capacity for limited axial play; and a steadying element with at least three substantially uniformly-spaced circumferentially-arranged spot projections adapted to coact with the non-rotating component to reduce the axial play of the non-rotating component in one direction during a portion only of each stitch-forming cycle and to normally oppose the axial thrust of the latter in the opposite direction to prevent canting of said non-rotating component in respect to the rotating component.

4. In a lockstitch sewing machine, feeding mechanism including a feed dog and mechanism for actuating it; stitch-forming mechanism including two relatively rotating components which are interconnected with capacity for limited axial play relatively; a steadying element with at least three substantially uniformly-spaced circumferentially-arranged spot projections adapted to cooperate with one of said components to normally oppose its end thrust in one direction and prevent it from tilting in respect to the axis of the other component; and interposed connections whereby said steadying element is actuated from the feed mechanism to reduce the axial play between the two components during a portion of each stitch-forming cycle.

5. In a lockstitch sewing machine, stitch-forming mechanism including an axially-hollow rotary hook component with an internal circumferential groove, an axially-hollow bobbin case holder capable of limited axial movement within the rotary hook component and having a narrower interengaging circumferential rib corresponding to the groove of the rotary hook component, and a bobbin case fitting within the bobbin case holder; a steadying element having at least three substantially uniformly-spaced circumferentially-arranged spot projections opposite the front face of the bobbin case; and means for actuating the steady element so that, through coaction between the spot projections on said element and the bobbin case, the bobbin case holder is moved periodically inward for reduction in the clearance between its rib and the rear side of the groove in the hook component during a portion only of each stitch-forming cycle, While at other times its outward thrust is onposed for maintenance thereof against canting in respect to the axis of said hook component, with its rib spaced from the front side of the groove in the hook component.

6. In a lockstitch sewing machine, stitch-forming mechanism including an axially-hollow rotary hook component with an internal circumferential groove, an axially-hollow bobbin case holder capable of limited axial movement within the rotary hook component and having a narrower interengaging circumferential rib corresponding to the groove of said rotary hook component, and a bobbin case fitting within the bobbin case holder, said bobbin case having reversely-beveled surfaces on its front face respectively at the top and bottom thereof; a steadying element having spot projections corresponding in position respectively with the upper and lower beveled surfaces at the front of the bobbin case; and means for actuating said steadying element so that through coaction between its spot projections and the beveled surfaces of the bobbin case, the bobbin case holder is periodically moved inward for reduction of the clearance between its rib and the rear side of the groove in the hook component during a portion of each stitch-forming cycle, while at other times its outward thrust is opposed for maintenance thereof against canting in respect. to the axis of said hook component with its rib spaced from the front side of the groove in the hook component.

7. In a lockstitch sewing machine, stitch-forming mechanism including a rotating component with a circumferential shoulder; a non-rotating component capable of limited axial movement relative to the rotating component and having a circumferential rib which is interrupted to provide a needle loop detaining horn; and a member for limiting outward axial play of the non-rotating component so that its rib is normally out of contact with the circumferential shoulder of the rotating component, said member having at least three spaced circumferentially-arranged spot projections between which and the non-rotating component, one limb of the needle loop is adapted to pass, one of said spot projections lying substantially in a plane which is radial to the axis of the rotating component and which extends through the end of a loop detaining horn.

8. In a locksmith sewing machine, stitch-forming mechanism including a rotating component with a circumferential shoulder; a non-rotating component capable of limited axial movement relative to the rotating component and having a circumferential rib which is interrupted to provide a needle loop detaining horn; and a member for limiting outward axial play of the non-rotating component so that its rib is normally out of contact with the circumferential shoulder of the rotating component, said member having at least three spaced circumferentially-arranged spot projections one of which is located at the downwardly moving side of said rotating component, as considered with regard to its normal rotation, in a plane above the axis of said rotating com-. ponent, between which projection and the nonrotating component one limb of the needle loop is adapted to pass.

9. In a lockstitch sewing machine, stitch-forming mechanism including a rotating component with a circumferential shoulder; a non-rotating component capable of limited axial movement relative to the rotating component and having a circumferential rib which is interrupted to provide a needle loop detaining horn; a member for limiting outward axial play of the non-rotating component so that its rib is normally out of contact with the circumferential shoulder of the rotating component, said member having at least three spaced circumferentially-arranged spot projections between which and the non-rotating component, one limb of the needle loop is adapted to pass, one of said spot projections lying substantially in a plane which is radial to the axis of the rotating component and which extends through the end of the loop detaining horn; and means for actuating the member for impartation of orbital movement to its spot projections in a plane parallel to that of the non-rotating component.

10. In a lockstitch sewing machine, stitchforming mechanism including a rotating component with an internal circumferential groove; a non-rotating component capable of limited axial movement relative to the rotating component and having an external circumferential rib engaging the groove of the rotating component, said rib being narrower than the groove and being interrupted to provide a needle loop detaining horn; and a member for limiting outward axial play of the non-rotating component so that its rib is normally out of contact with both sides of the groove in the rotating component, said member having at least three spaced circumferentially-arranged spot projections between which ponent with an internal circumferential groove;

a non-rotating component capable-of limited axial movement relative to the rotating component and having an external circumferential rib engaging the groove of the rotating component, said rib being narrower than the groove and being interrupted to provide a needle loop detaining horn; a member for limited outward axial play of the non-rotating component so that its rib is normally out of contact with both sides of theigroove in the rotating component, said member having three spaced circumferentially-arranged spot projections betweenwhich and the non-rotating component the needle loop thread is adapted to pass, one of said projections lying substantially in a plane which is radial to the axis of the rotating component and which extends through the end of the loop-detaining horn; and means for actuating the member for impartation of orbital movement to its spot projections in a plane parallel to that of the nonrotating component.

12. In a lockstitch sewing machine, a reciprocating needle; complemental stitch-forming means including a rotating component which is adapted to revolve twice for each reciprocation of the needle, and which has a circumferential shoulder, and a non-rotating component capable of limited axial movement relative to the rotating component and having a circumferential rib which is interrupted to provide a needle loop detaining hom and a member for limiting outward axial play of the non-rotating component so that its rib is normally out of contact with the circumferential shoulder of the rotating component, said member having at least three spaced circumferentially-arranged spot projections between which and the non-rotating com ponent, one limb of the needle loop is adapted to pass, one of said projections lying substantially in a plane which is radial to the axis of the rotating component and which extends through the end of the loop detaining horn.

13. In a lockstitch sewing machine, a reciprocating needle; a complemental stitch-forming means including a rotating component which is adapted to revolve twice for each reciprocation of the needle and which has an internal circumferential groove, and a non-rotating component capable of limited axial movement relative to the rotating component and having an external circumferential rib engaging the groove of the rotating component, said rib being narrower than the groove and being interrupted to provide a needle loop detaining horn; and a member for limiting outward axial play of the non-rotating component so that the rib of the latter is normally out of contact with both sides of the groove in the rotating component, said member having at least three spaced circumferentiallyarranged spot projections between which and the non-rotating component, one limb of the needle loop is adapted to pass, one of said projections lying substantially in a plane which is radial to the axis of the rotating element and which exgroove and being interrupted to provide a needle I loop detaining horn, and a bobbin case within the holder: and a member for limiting outward axial play of the bobbin case holder so that the rib of the latter is normally out of contact with both sides of the groove in the rotary hook, said member having at least three circumferentiallyarranged spot projections between which and the front of the bobbin case, one limb of the needle loop is adapted to pass, one of said projections lying substantially in a plane which is radial to the hook axis and which extends through the end of the loop detaining horn.

15. In a lockstitch sewing machine, a reciprocating needle; complemental stitch-forming means including a rotating component which is adapted to revolve twice for each reciprocation of the needle, and which has a circumferential shoulder, and a non-rotating component capable of limited axial movement relative to the rotating component and having a circumferential rib which is interrupted to provide a needle loop detaining horn; a member for limiting outward axial play of the non-rotating component so that its rib is normally out of contact with the circumferential shoulder of the rotating component, said member having at least three spaced circumferentially-arranged spot projections between which and the non-rotating component, one limb of the needle loop is adapted to pass, one of said projections lying substantially in a plane which is radial to the axis of the rotating component and which extends through the end of the loop detaining horn; and means for actuating the member for impartation of orbital movement to its spot projections in a plane parallel to that of the non-rotating component.

16. In a lockstitch sewing machine, stitchforming mechanism including a rotating component with an internal circumferential groove; a non-rotating component capable of limited ain'al movement relative to the rotating component and having an external circumferential rib engaging the groove of the rotating component, said rib being narrower and of somewhat smaller diameter than the groove and being interrupted to provide a needle loop detaining horn; and a member for limiting outward axial play of the non-rotating component so that its rib is normally out of contact with both sides of the groove in the rotating component, said member having at least three spaced circumferentially-arranged spot projections between which and the nonrotating component the needle loop thread is adapted to pass, one of said projections lying substantially in a plane which is radial to the axis of the rotating component and which extends through the end of the loop detaining horn.

1'1. A look stitch sewing machine comprising a needle; feeding mechanism including a moving" member, means for actuating the moving member, and means whereby the movements of the member may be adjusted for variation of stitch length without change in the timing thereof in respect to the movements of the needle; complemental stitch forming mechanism including two relatively rotatable components which normally have capacity for limited axial play; and means connected to the moving member of the feeding mechanism for taking up the axial play between the aforesaid components during a portion of each stitch forming cycle including a steadying element which contacts with one of said components at at least' three substantially uniformly spaced circumferential points.

18. A losk stitch sewing machine comprising a needle; feeding mechanism including a moving member, means for actuating the moving member, and means whereby the movements of the member may be reversed without change in the timing thereof in respect to the movements of the needle; complemental stitch forming mechanism including two relatively rotatable components which normally have capacity for limited axial play; and means connected to the moving member of the feed mechanism for taking up the axial play between the aforesaid components during a portion of each stitch forming cycle, including a steadying element which contacts with one of said components at at least three substantially uniformly spaced circumferential points.

19. In a lockstitch sewing machine, a rotating component having an internal circumferential groove; a non-rotating floating component having an interengaging circumferential rib whereof the width and the diameter are somewhat less than the width and diameter of said groove, and

whereby the two components are held assembled with capacity for restricted relative movement in the direction of their axes as well as in a direction transversely of their axes; and means operative to cause the axial play between said components to be substantially taken up during a portion of each stitch forming cycle.

20. In a lock stitch sewing machine, stitchforming mechanism including two substantially coaxial relatively rotating components which are interconnected with capacity for limited relative play both axially and transversely of their axes; and means operative to cause theaxial play between said components to be substantially taken up during a portion of each stitch forming cycle.

21. In a lock stitch sewing machine, stitchforming mechanism including an axially hollow rotary hook with an internal circumferential groove; a non-rotary bobbin case holder with a circumferential rib engaging the groove of the rotary hook, said rib being slightly narrower and of slightly smaller diameter than the groove so that the holder has capacity for limited relative 

